Mobile ad-hoc networks (MANET's) are becoming increasingly popular because they operate as self-configuring networks of mobile routers or associated hosts connected by wireless links to form an arbitrary topology. The routers, such as wireless mobile units, can move randomly and organize themselves arbitrarily as nodes in a network, similar to a packet radio network. The individual units require minimum configuration and their quick deployment can make ad-hoc networks suitable for emergency situations. For example, many MANET's are designed for military systems such as the JTRS (Joint Tactical Radio System) and other similar peer-to-peer or Independent Basic Service Set systems (IBSS).
TDMA technology is becoming more popular for use in these mobile ad-hoc network systems. In an ad-hoc network using a TDMA communications protocol, channel access scheduling is a platform of the network structure. Some problems are encountered with distributed channel scheduling used in a multi-hop broadcast networks. As known to those skilled in the art, the optimum channel scheduling problem is equivalent to the graph coloring problem, which is a well known NP-complete problem, cited in numerous sources. Many prior art systems assume that the network topology is known and is not topology transparent.
Physically, a mobile ad-hoc network includes a number of geographically-distributed, potentially mobile nodes sharing a common radio channel. Compared with other types of networks, such as cellular networks or satellite networks, the most distinctive feature of mobile ad-hoc networks is the lack of any fixed infrastructure. The network may be formed of mobile nodes only, and a network is created “on the fly” as the nodes transmit with each other. The network does not depend on a particular node and dynamically adjusts as some nodes join or others leave the network.
The standards governing Wireless Local Area Networks (WLANs) networking products are defined by a suite of specifications issued by the IEEE and known as the IEEE 802.11 standard, incorporated herein by reference in their entirety. The standards define the operation of both the radio PHY layer and the MAC layer including a synchronization mechanism. The synchronization mechanism is used to provide a uniform time base.
For ad-hoc networks, the timing synchronization is typically implemented using a distributed algorithm that is performed by the member nodes. Each node typically transmits beacons in accordance with an algorithm defined in the 802.11 standard. Each node adopts the timing received from any beacon or probe response that has a timing synchronization function value later than its own timer.
One principle of wireless communications environments using TDMA protocols is changes in the propagation can cause an unsophisticated protocol or waveform to cease in delivering data or effect the packet error rate (PER) efficiently. Usually some systems use Automatic Repeat Request (ARQ) algorithms that improve deliver at a cost of latency and additional network load. In some TDMA ad-hoc networks, it is expected that each node in the network could be moving and connections between nodes would vary in availability and quality. An adaptive data rate algorithm would maintain these link changes by optimally selecting data rate and route for successful packet delivery. The performance is typically no better than what the physical channel can handle, and therefore, it is desirable to determine dynamically an access point to produce a much higher performance system.
Rate adaptation has been used in past TDMA ad-hoc systems such as FS-1052 and STANAG-5066, using data traffic and demodulation statistics between two nodes that currently exchange data. It is possible that some of these systems also used long-term storage of previous observation results to help predict initial waveform selection. Many issues prevent a prediction mechanism using long-term historical data from being successful on the first transfer attempt. As data traffic commences, these algorithms adapt to track the channel depending on how fast the channel changes.